Biomedical subjects
R N Chatterjee
Publications and source records attributed to R N Chatterjee.
Gel diffusion analysis of host preference pattern of Anopheles subpictus in West Bengal, India.
Host preference pattern of Anopheles subpictus was studied from cattlesheds and human dwellings of Uttarpara, Hooghly, West Bengal using a modified gel diffusion technique. Our results reveal that An subpictus is becoming less zoophagic in this area.
Binding affinity of leucine-containing chromatin proteins to the polytene X chromosome of Drosophila hydei and its significance.
Association of newly synthesised non-histone chromosomal protein to the polytene X chromosome of larval salivary glands of D. hydei has been examined by autoradiographic procedure using 3H-leucine. It has been observed that 3H-leucine labelling pattern is inhibited in presence of puromycin. Results further reveal that there is a reasonable concordance between the binding affinity of newly synthesized protein on the single X chromosome of the male and paired X's of the female. A sitewise analysis of 3H-leucine labelling reveals that although 3H-leucine incorporation pattern are not strictly comparable with 3H-RNA synthesis pattern observed under in vivo transcription condition, the labelling pattern with 3H-leucine are not merely the reflection of mass distribution of protein in the polytene chromosomes. Certain aspects of regulation in the organisation of male and female X chromosome in Drosophila by de novo synthesis of protein are discussed.
Mosaic pattern of X-chromosomal transcription in a strain of Drosophila melanogaster with aneuploid X chromosome.
Organisation and template activity pattern of salivary gland chromosomes of a segmental male aneuploid of D. melanogaster, carrying duplication for the segment 8C-20F of X chromosome, have been examined by in situ transcription. In an earlier study [Chatterjee, Chromosoma 91 (1985) 259], it was suggested that in male aneuploids, up to an additional length of 8C-20F, the template activity of X chromosome tends to remain at a male level and beyond that level shifts towards female level. A large scale search of the template activity pattern of the aneuploid carrying dp.(8C-20F) clearly indicates that presence of the duplication fragment to X in the normal karyotype (1X2A) lead to a varying degree of condensation of euchromatic regions of entire X chromosome (X + X fragment 8C-20F) starting from 'male' level, over a wide range of 'intermediate' level to a normal 'female' level. In this study, the individual cells of the aneuploid appeared to display their own state of X condensation and transcription. Although in the aneuploid, X chromosomal activity is not determined by a purely quantitative effect of X vs. autosomal material (X:A ratio = 0.81), the 8C-20F segment of X chromosome must contain some major elements concerned with the signal given by X:A ratio for X chromosome differentiation.
The LSP1-alpha gene of Drosophila melanogaster exhibits dosage compensation when it is relocated to a different site on the X chromosome.
The LSP1-alpha gene of Drosophila melanogaster is located on the X chromosome at 11B yet is not dosage compensated. In order to determine if this gene is inherently incapable of dosage compensation or if it does not compensate because the appropriate regulatory cis-acting sequences are absent from its chromosomal domain, we have undertaken to relocate it to ectopic sites on the X chromosome. To differentiate between the transcripts produced by the transduced gene and those produced by the indigenous gene, we inserted a 500-bp sequence of mouse DNA into the LSP1-alpha clone prior to using it for transformation. Our results show that the LSP1-alpha gene exhibits equivalent levels of transcripts in the two sexes when it is relocated to either an autosomal site or to an ectopic site on the X chromosome. We conclude that the LSP1-alpha gene is capable of dosage compensation.
Application and efficiency of scintillation autoradiography for Drosophila polytene chromosomes.
A rapid method of autoradiography using the scintillation cocktail (Toluene and scintillation fluid, Omnifluor) has been described earlier. Its application and efficiency have been tested using both 3H-thymidine and 3H-urine. The optimum time required for processing the autoradiograms has been found to be 24 h dry exposure followed by 48 h in the scintillation mixture. Detailed analysis of the autoradiograms with 3H-uridine reveals that with the rapid method the 100% level of labelling index is reached by 48 h while with the conventional method the same level is reached by 10 to 12 days of dry exposure. The maximum grain density is reached by 16 to 17 days by the conventional method. While by the rapid method, the maximum grain density is approximately 80% of the control, this grain density is reached by 48 h (plus 24 h of dry exposure) and thereafter forms a plateau. With Toluene alone the grain density never exceeds 20%. The background is also relatively low and less variable in the O-T-processed autoe scintillation fluid plays the key role in augmenting the labelling. Furthermore, although the maximum grain density by the rapid technique is 80% of the control, the grain density obtained by the rapid method gives less coincidence and superimposition of grains. On the other hand, with 3H-thymidine, although all labelling patterns could be resolved, the labelling index (i.e., percent of labelled cells) is about 40% at 48 h (plus 24 h) and about 79.5% at 96 h with the rapid method, as compared to about 30% and 44% with the conventional method at the two time points, respectively. Only with 16--17 days' dry exposure the 3H-thymidine labelling index increases to 67%. The frequency of the initial patterns (DD-2C) which are usually less frequency, has been found to have increased with the rapid method. No difference in grain density of labelling of 3H-thymidine could be detected between the rapid method and the conventional method. The resolution of grains also seems to be better by the rapid method, due probably to smaller size and lack of superimposition of grains. Other applications, advantages and limitations have been discussed.
Chromosomal basis of dosage compensation in Drosophila. IX. Cellular autonomy of the faster replication of the X chromosome in haplo-X cells of Drosophila melanogaster and synchronous initiation.
[(3)H]Thymidine labeling patterns have been examined in gynandric mosaic salivary glands of drosophila melanogaster. The Ring-X stock, R(1) w(ve)/In(1)dl 49, l (1) J1 y w lz(s), was used for this purpose. 365 labeled XX2A and 40 labeled XO2A nuclei were obtained from a total of 624 nuclei in nine pairs of mosaic salivary glands. It was observed that in all but those nuclei which had DD, 1C, and 2C patterns, the X chromosome of the XO2A nuclei always had fewer sites labeled than the X chromosomes of the XX2A nuclei, for a given pattern of the autosomes in either sex. Such asynchronous labeling of the X chromosome in the XO2A (male) nuclei was observed regardless of the proportion of the XO2A cells (2.0-73.7 percent), in the mosaic glands. Moreover, while the frequency of [(3)H]thymidine labeling for all of the 39 replicating units except the two late replicating sites (3C and 11A) in the X chromosome of the XO2A nuclei, was consistently lower than in the X chromosome of the XX2A nuclei, the mean number of grains on the X chromosome was relatively (to autosomes) similar in both XX2A and XO2A cells. The results, therefore, suggest that, as in XY2A larval glands, the X chromosome in the XO2A cells also completes the replication earlier than autosomes and that the XO2A nuclei show cellular autonomy with respect to the early replication of the X chromosome, like its counterpart, RNA transcription. Absence of the asynchrony during the initial phase (DD-2C) further completes the replication earlier but that the rate of replication of its DNA is possibly faster, and (b) that there might be a common regulation with respect to the initiation of replication of different chromosomes in a genome.
Inhibition of initiation of DNA replication in Drosophila by alpha-amanitin & its possible significance.
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A rapid autoradiographic technique for chromosomal squash preparations.
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